This invention relates to a refill cartridge for a liquid filter.
The fuel supply for a compression ignition engine must be kept clean of particulate contaminants to assure proper operation of the engine. Accordingly, a liquid filter is normally installed in the fuel line of a compression ignition engine to assure that all contaminants will be removed from the fuel supply. Because of the sensitivity of the compression ignition engine to contaminants, the filter must be relatively sophisticated. It must also be possible to change the filtering medium periodically. One type of fuel filter used in such an application is disclosed in U.S. Pat. Nos. 3,591,004 and 3,630,382. One difficulty with the fuel filter disclosed in these patents is the fact that is uses a glass housing which holds the filtering medium. In order to assure proper sealing between the medium and the housing, it has been customary to provide refill cartridges which consist of the glass housing, the filtering medium sealed within the housing, and a base or cover member. However, since the glass housing, which is relatively expensive, must be replaced each time the filter cartridge is changed, this type of filter cartridge is relatively expensive. The glass housing must be used in order to withstand the relatively high internal pressures generated during use of the filter, and also to assure that the filtering medium is properly sealed to guard against bypass of contaminated fuel around the filtering medium.
Accordingly, the present invention provides a liquid filter for use in the fuel supply system for a compression ignition engine that provides a plastic bladder or blister which fits within the conventional glass housing used in the prior art. In this way, the filtering medium can be sealed within the blister, which would normally rupture if used alone in the relatively high pressure environment of the liquid filter. However, since the blister conforms exactly with the shape of the glass housing, the latter supports the blister to take the internal forces generated by the fluid pressure of the liquid.